FANUC 16i/18i/21i hardware connection and troubleshooting

2.2 Power on and power-off sequence

To ensure reliable system startup and avoid data errors, the recommended power on sequence is:

Machine tool main power supply (200VAC), separate detector (grating ruler) power supply

I/O Link slave station, separated detector interface unit, independent LCD unit (24VDC), servo amplifier control power supply (200VAC)

CNC control unit (24VDC)

When powered on, 1 and 2 should be completed within 500ms after 3 are powered on. The power-off sequence is the opposite: first cut off the 24V of the CNC, and then cut off other units. If the timing is violated, there may be residual alarm information in NC.

2.3 Battery Replacement: Memory Backup and Absolute Position Battery

FANUC CNC uses multiple batteries, and the most common problem on site is SRAM data loss or absolute position loss caused by low battery voltage.

(1) CNC memory backup battery (3VDC)

Model: Lithium battery A02B-0200-K102 (pre installed on CNC front panel)

Replacement timing: When the display screen flashes the "BAT" alarm, it should be replaced within 2-3 weeks (depending on the configuration). It is recommended to replace it proactively once a year.

Replacement steps (hot replacement):

Keep the CNC powered on for at least 30 seconds (charging the capacitor)

Turn off the CNC power supply

Unplug the old battery connector and remove the battery

Insert and connect a new battery within 30 minutes (for 16i/18i/21i series, memory data can be retained for 30 minutes after battery removal)

Power on again and clear the alarm

External battery box: Two D-type alkaline batteries (A02B-0236-C281) can be used instead of lithium batteries, and the CNC also needs to be powered on during replacement.

(2) Absolute pulse encoder battery (6VDC, used for separate detectors or motors with built-in absolute encoders)

Separate absolute encoder: using 4 D-type alkaline batteries (in series). When APC alarm 3n6~3n8 occurs, it should be replaced as soon as possible (within 1-2 weeks). When replacing, it is necessary to keep the CNC powered on, otherwise the absolute position will be lost.

The motor is equipped with an absolute encoder: the battery is installed on the servo amplifier. Please refer to the α i series maintenance manual.

I/O module and signal connection: from I/O Link to DI/DO

FANUC CNC connects distributed I/O modules (such as connection type I/O modules, operation panel I/O modules, etc.) through the I/O Link serial bus. Proper wiring and address allocation are key to avoiding on-site signal misoperation.

3.1 I/O Link Cable and Transmission Distance

Electrical signal cable: up to 10m in length (can be extended to 15m if all are in the same cabinet). Use recommended shielded twisted pair cables (such as A66L-00001-0284 # 10P).

Fiber optic cable: When longer distances or strong interference environments are required, use optical I/O Link adapters (A13B-0154-B001/B002). The total length can reach 200m (standard type) or 100m (high-speed type). Up to 16 high-speed adapters (or 5 standard adapters) can be cascaded.

3.2 DI/DO Module Wiring Example (Taking Connection Type I/O Module as an Example)

DI (Input): The module provides 24 input points/module (basic module+expansion module up to 96 points). The input voltage is 24VDC, the ON voltage is ≥ 14V, and the OFF voltage is ≤ 6.5V. The response time includes receiver delay (≤ 2ms)+I/O Link transmission time (≤ 2ms)+ladder scan period.

DO (Output): The maximum load current at each point is 200mA (continuous), and the saturation voltage drop is ≤ 1V. It is important to note that the total current of the DOCOM pin does not exceed 0.7A. The DO driver has overcurrent and overheat protection, and once triggered, the corresponding output byte will be forcibly turned off, and the corresponding alarm bit (such as Xm+15) in the DI address will be set to 1.

Important notice: For 24VDC input modules, DICOM generally recommends connecting to 0V (source input mode) to avoid mistaking the input as ON due to a short circuit to ground. The emergency stop signal must be assigned to a fixed address on the common terminal (such as Xm+1. x or Xm+2. x, etc.), and cannot be assigned to an address that allows the selection of the common ground (can be connected to+24V), otherwise there may be safety hazards.

3.3 Connection of manual pulse generator (handwheel)

The handwheel uses a 5V power supply, and due to voltage drop in the cable, the maximum length needs to be calculated. Formula: 0.2V ≤ 0.1A × R × 2L/m, where m is the number of 5V and 0V cores. When using the recommended cable A66L-00001-0286 (6 power cords), the maximum length of a single handwheel is approximately 76m (but FANUC limits it to ≤ 50m); About 38m with two handwheels.

Servo and spindle interface: Fiber optic serial bus (FSSB and serial spindle)

4.1 Servo Interface (FSSB)

The CNC and α i series servo amplifiers are connected through optical cables (COP10A interface). A single optical cable can control up to 8 axes (16i), 6 axes (18i), or 4 axes (21i). The total length of the optical cable is ≤ 100m, and the distance between units is ≤ 10m (using inner cables) or ≤ 100m (using reinforced outer cables).